This application builds upon the specifications filed in U.S. application Ser. Nos. 13/420,526 and 13/420,532, both filed Mar. 14, 2012, both of which are herein incorporated by reference.
A number of techniques have been developed to attack a lock. One method of attack is to overtorque a handle using, for example, a long wrench. Overtorquing a handle causes internal components to break. Depending on the design of the lock, this can enable an intruder to open the door. Another method is to strike the lever arm in one direction, and then jerk it back in another, rapidly enough or repeatedly enough to work the door components free.
To disable such methods of attack, U.S. Pat. No. 5,794,472 to Best discloses a locking lug with a shear line or frangible section that shears if the outside door handle is overtorqued. Shearing off the locking lug does not, however, prevent key cylinder rotation. Best requires an outside door handle that is configured to engage the door frame, and prevent further rotation, after the outside door handle has been rotated to about 93°. Accordingly, this solution would not work on typical out swinging doors, which are common in many public buildings, like classrooms, in order to meet fire code egress requirements. Best also requires a thick cast steel outer hub to house the locking lug, key cylinder, and an associated lost motion drive member.
The present invention described below can be characterized in many different ways, not all of which are limited by its capacity to address the above-mentioned issues, needs or design constraints.